The disclosed embodiments of the present invention relate to recording data onto an optical storage medium, and more particularly, to a method for recording critical patterns with different mark lengths onto an optical storage medium (e.g., an optical disc) and related controller thereof.
Data patterns recorded onto an optical storage medium may be simply categorized into marks each representative of a series of 1's and spaces each representative of a series of 0's. In general, the recording of a mark requires higher laser power levels, whereas the recording of a space requires lower laser power levels. For example, the optical storage medium may be recorded using a plurality of laser power levels, such as a peak laser power level Ppeak, a middle laser power level Pmiddle, a space laser power level Pspace, and a bottom laser power level Pbottom. It should be noted that Ppeak>Pmiddle>Pspace>Pbottom. The power transition from one of the laser power levels to another of the laser power levels may affect the formation of a mark on the optical storage medium. For example, the power transition from a lower laser power level to the peak laser power level Ppeak (i.e., the highest laser power level) for the first time after the laser power is lately lowered to the bottom laser power level Pbottom (i.e., the lowest laser power level) and the power transition from a higher laser power level to the bottom laser power level Pbottom (i.e., the lowest laser power level) for the first time after the laser power is lately raised to the peak laser power level Ppeak (i.e., the highest laser power level) are critical to form a mark on the optical storage medium. Thus, the timing of these critical power transitions may dominate the accuracy of the length of the mark formed on the optical storage medium.
An optical pick-up unit (OPU) is used for generating a laser beam with a desired laser power level for recording data patterns, including marks and spaces, onto an optical storage medium. In general, the optical pick-up unit is coupled to a controller chip via an interface disposed therebetween. The controller chip is configured to generate control signals, such as one or more sets of write enable (WEN) signals, to the OPU for setting the laser power level used by the OPU. Regarding a conventional controller chip design, the recording of a first mark (e.g., a 2T mark) and the recording of a second mark (e.g., a 3T mark) may employ different control signals (i.e., different WEN signals) to enable the laser beam radiated from the OPU to have the power transition from a lower laser power level to the peak laser power level Ppeak (i.e., the highest laser power level) for the first time after the laser power is lately lowered to the bottom laser power level Pbottom (i.e., the lowest laser power level). Further, the recording of the first mark (e.g., a 2T mark) and the recording of the second mark (e.g., a 3T mark) may employ different control signals (i.e., different WEN signals) to enable the laser beam radiated from the OPU to have the power transition from a higher laser power level to the bottom laser power level Pbottom (i.e., the lowest laser power level) for the first time after the laser power is lately raised to the peak laser power level Ppeak (i.e., the highest laser power level). In a case where there are non-ideal effects present at the controller chip, the OPU, and/or the interface between the controller chip and the OPU, the difference between actual lengths of the first mark and the second mark formed on the optical storage medium may be significantly deviated from an expected value, which results in degradation of the recording quality.